1. Field of the Invention
The present invention relates to a bonded body of a ceramic member and a metal composite member, and to a wafer support member that uses the same. The present invention also relates to a method of processing a wafer that employs the wafer support member of the present invention.
2. Description of the Related Art
For example, a film deposition apparatus or an etching apparatus is used to manufacture semiconductor chips. In such an apparatus, for example, an electrostatic chuck that utilizes electrostatic attraction to hold a wafer or an electrostatic chuck provided with a heater that heats a wafer while holding it is used as a wafer support member that holds the semiconductor wafer.
The electrostatic chuck is such a wafer support member that has electrostatic chucking electrode disposed inside of the wafer support member or on a surface opposite to a wafer mounting surface for the purpose of firmly holding the wafer during treatment, so as to attract the wafer onto the mounting surface by Johnson Rahbeck effect or Coulomb effect obtained by applying a voltage across the electrostatic chucking electrode.
The electrostatic chuck provided with heater is such a wafer support member that has enhanced function of heating the wafer due to the heating electrode disposed inside of the wafer support member or on a surface opposite to a wafer mounting surface so as to heat the wafer uniformly.
In the processes of treating semiconductor wafers (hereinafter referred to simply as wafer) for manufacturing semiconductor devices such as PVD, CVD, sputtering, SOD, SOG and other film deposition process and etching process, it is important to form a film having uniform thickness and homogeneity on the wafer or to etch the film that has been formed with uniform depth.
The wafer support member comprises a plate-shaped ceramic member of which of main surface is used as an attracting surface (mounting surface) whereon the wafer is held, and a metal-ceramics composite member (plate-like member) that is bonded to the surface of the plate-shaped ceramic member opposite to the attracting surface, where the metal-ceramics composite member is cooled by a cooling medium in order to quickly remove the heat generated in the wafer during treatment by means of plasma.
A wafer support member (electrostatic chucking stage) having such a structure as described above is described in, for example, Japanese Unexamined Patent Publication (Kokai) No. 10-32239. As shown in a sectional view of FIG. 5, the electrostatic chucking stage 50 described in patent document 1 is constituted by joining a plate-shaped sintered ceramic member 51 having an electrostatic chucking electrode 52 embedded therein and a composite plate 55 (metal-ceramics composite member) made of ceramics and aluminum by means of a bonding layer 54. Japanese Unexamined Patent Publication (Kokai) No. 10-32239 discloses the use of solder or brazing material as the bonding layer 54.
With the conventional bonded body of between the ceramic member and the metal-ceramics composite member in the wafer support member of the prior art, however, there has been such a problem that exposed surface surrounding the bonding layer 54 is exposed to plasma during the process of forming or etching the film on the wafer by means of plasma, thus resulting in the erosion of the bonding layer 54 between the ceramic member and the metal-ceramics composite member.
The erosion of the bonding layer 54 may, in the worst case, cause the ceramic member to come off the metal-ceramics composite member.
Specifically, as shown in sectional view of FIG. 6, a bonded body 60 consisting of the ceramic member 61 and the metal-ceramics composite member 65 has a site G of the maximum shear stress at the center of a brazing material layer 63, and an erosion pit is produced in the portion of G as shown in FIG. 6 when the site G of the maximum shear stress is eroded by plasma. Since the erosion pit is a very sharp defect, it acts together with the maximum shear stress so as to tear off the brazing material layer 63 that is the bonding layer, thus causing the ceramic member 61 to come off the metal-ceramics composite member 65. In this way, as the site G of maximum shear stress generated at the center of the brazing material layer 63 is exposed to plasma and eroded thereby, the bonding layer (brazing material layer 63) is significantly damaged by the bonded effects of the erosion pit and the maximum shear stress, thus resulting in destruction of the bonded body 60.
In the bonded body 60, a metal layer 62 is formed on one of main surfaces of a ceramic member 61, and a metal layer 64 is formed on one of main surfaces of the metal-ceramic composite member 65, while the metal layers 62 and 64 are joined together by means of the brazing material layer 63.